The canyon, made by the Yellowstone River, which continues to carve its path through the mountains, reaches a maximum depth of 1,540 feet a short distance down-river from Artist Point. The colors are wonderful and ever-changing. From the black rock near the top of the canyon, the river has cut through many layers of the same rhyolite that forms so much of the park. It is naturally gray or light pink and lavender, but iron compounds in varying amounts have stained it shades of orange and yellow - the yellow stone that gave a name to the river and the park.